Most Texas residents are aware of two primary scientific tests, blood and breath, used by law enforcement as evidence to support a DWI charge. However, what may not be evident is the very different procedural aspects of these two tests and the implications on the laws governing their use.
Law enforcement professionals have argued that blood tests result in more plea bargains and less need for expensive trials, thereby saving money. However, opponents suggest that the process of using blood tests after a stop causes the officer to be off the street for far more hours after the stop than a breath test, handling onerous paperwork to facilitate the blood test and its subsequent evidentiary use. The proponents have countered that a trial can take the officer into the courtroom and off the street for far more hours than that required for a blood test. As such, the avoidance of trial that is more likely with a blood test than a breath test may outweigh the time cost involved on the night of the stop and related blood testing.
Making the issue more complicated, the United States Supreme Court recently held in a 4th Amendment case that there must be a search warrant in order to require a driver take a blood alcohol test, while such a warrant is not required for a breath test. While this ruling has bearing on how and whether a particular department will be using blood tests instead breath tests, it also has the additional repercussion of limiting the criminality some states apply to drivers who refuse alcohol testing.
For now, it would appear that without a search warrant providing the state the right to a blood test, there can be no criminality applied to a driver who refuses a blood test when there is no search warrant.